$NetBSD: patch-efence_c,v 1.1 2012/06/16 07:46:55 dholland Exp $

Add memory barriers for gcc around recursive calls to malloc and free
with "internalUse" set to 1. gcc fervently believes that malloc and
free do not interact with anything else, and so it freely reorders code
around calls to malloc. This causes internalUse to not be set to 1
during the recursive call, which results in an infinite recursion.

Compare patch-bm in editors/emacs20.

--- efence.c~	2002-02-19 22:10:46.000000000 +0000
+++ efence.c
@@ -377,7 +377,16 @@ allocateMoreSlots(void)
 	noAllocationListProtection = 1;
 	internalUse = 1;
 
+#ifdef __GNUC__
+	__asm __volatile("":::"memory");
+#endif
+
 	newAllocation = malloc(newSize);
+
+#ifdef __GNUC__
+	__asm __volatile("":::"memory");
+#endif
+
 	memcpy(newAllocation, allocationList, allocationListSize);
 	memset(&(((char *)newAllocation)[allocationListSize]), 0, bytesPerPage);
 
@@ -386,8 +395,16 @@ allocateMoreSlots(void)
 	slotCount += slotsPerPage;
 	unUsedSlots += slotsPerPage;
 
+#ifdef __GNUC__
+	__asm __volatile("":::"memory");
+#endif
+
 	free(oldAllocation);
 
+#ifdef __GNUC__
+	__asm __volatile("":::"memory");
+#endif
+
 	/*
 	 * Keep access to the allocation list open at this point, because
 	 * I am returning to memalign(), which needs that access.